What are they building on Celo?

ChainBridge

The purpose of the grant was to extend ChainBridge to support Celo. ChainBridge facilitates the transfer of value and data between private and public Celo chains as well as other EVM compatible blockchains. Once completed, ChainBridge's Substrate Pallet will allow Celo to bridge to Substrate based chains as well. This work is extremely valuable to Celo’s mission of building an open monetary system as it enables the seamless transfer of value and information between Celo private & public chains, as well as other blockchain ecosystems.